1970 FIAT 500L Running Issues

My neighbor recently had a 1970 Fiat 500L imported from Italy. Car looks wonderful and apparently ran OK before it was shipped to the US but since it arrived at my buddys house it has never run.
Engine is a whopping 650cc with 2 cylinders.

I first looked at it last night and found that the battery was connected in reverse polarity. Swapped that and no difference. Next thing I spotted was the main coil lead was actually plugged into one of the spark plug outlets on the dizzy cap instead of the center connector. Fixed that and still not running. With all these little issues resolved, I started basic troubleshooting. I traced 12V from the battery (in the front) to the engine (in the rear) to a relay box on the rear firewall. The relays have been bypassed as the original dynamo was swapped out for an alternator. However I only get 9v at the alternator. I traced the cable and found the conductor was broken inside the insulation. I made up a new cable and had 12v at the alternator. As if by magic the car starts and runs for about 2 mins. I nearly made it to step 6 before the engine died from what sounded like fuel starvation but who knows. During the 2 mins of running I measured the voltage coming off the alternator which was about 13.5V. Not bad for idle. I am thinking the alternator is most likely undamaged from the reversed polarity episode.

When it won't start I have checked the spark and it looks strong. I also checked the gas by disconnecting the fuel line and watched it pump gas into a container as the engine was cranked. Spark plugs are new.

I tried spraying some starter spray in the intake which didn't make any difference. At this stage my mind is saying the problem is fuel related but since it ran for a couple of minutes I don't thing there is a blocked jet. I did pull the fuel filter from the carb and it was as clean as whistle.

The electricals on this sound like a complete ifdiot touched it, or someone tried to sabotage the car.

1) Is this car originally a negative-ground car? The USA had a few positive ground vehicles, but they were early, like the 1930's. I do not know about European cars. I just found that the Mini was positive ground up through 1969.
2) When a car is changed from a generator to alternator, wiring changes are needed. The following link MAY help with that.HOW TO CONVERT FROM GENERATOR TO ALTERNATOR
3) I assume this car has a point style ignition. There MAY be some type of resistor in the ignition circuit to keep the points from burning too fast. That may or may not have been removed.
4) The coil may be old and damaged and that's why it's running only for a few minutes before the coil overheats or has an issue.

The Fiats are known for horrible electrical problems.

Yes, check/change your fuel filter
Change the gasoline in it. Make sure you use NON-ethanol.
Does the carburetor need to be cleaned?

You state that it was running prior. How long ago and how well? That is comparable to "It ran when I parked it....45 YEARS ago....."

The electricals on this sound like a complete ifdiot touched it, or someone tried to sabotage the car.

1) Is this car originally a negative-ground car? The USA had a few positive ground vehicles, but they were early, like the 1930's. I do not know about European cars. I just found that the Mini was positive ground up through 1969.
2) When a car is changed from a generator to alternator, wiring changes are needed. The following link MAY help with that.HOW TO CONVERT FROM GENERATOR TO ALTERNATOR
3) I assume this car has a point style ignition. There MAY be some type of resistor in the ignition circuit to keep the points from burning too fast. That may or may not have been removed.
4) The coil may be old and damaged and that's why it's running only for a few minutes before the coil overheats or has an issue.

The Fiats are known for horrible electrical problems.

Yes, check/change your fuel filter
Change the gasoline in it. Make sure you use NON-ethanol.
Does the carburetor need to be cleaned?

You state that it was running prior. How long ago and how well? That is comparable to "It ran when I parked it....45 YEARS ago....."

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Thanks dude for chiming in on this. The car is, and as far as I know, always was a negative earth. It definitely has been converted from a dynamo to an alternator and I can only assume the wiring has been done correctly - Ignition lights come on, starter motor turns and the engine will start so I imagine most electrical stuff is fundamentally OK. The coil looks newish and gives a decent spark on my tester - even when it won't start the spark looks strong. Ignition is points based but again I can't see anything wrong with them.

The owner drained the gas from the tank 2 weeks ago when he bought it (not sure about it being ethanol free). Yesterday I dismantled the carb and gave it a good clean. I noticed that the reservoir bowl had no gas in it when I stripped it down so I double checked the float valve and also tested the fuel pump. I put a new fuel filter in it for good measure. I was pretty sure I had found and fixed my problem (I hadn't). Another thing I did notice on the carb was the fuel return from the reservoir had been capped by a blocking pipe. Not sure why someone would do this but I could not find any evidence of a return line going back to the fuel tank so I assumed it wasn't a recent thing. After all my efforts yesterday the car started strongly as normal, ran well at idle and revved responsively before it started to die around 30-60 seconds later. It never started again during my visit. The neighbor told me it fired right up about 2 hours later and again died. It is like the fuel reservoir fills up after a couple of hours and then the car only runs on the fuel that is in that tiny reservoir - as soon as that runs out it stalls. Of course I can not think of any logic to back that theory up (how would a reservoir fill up with the pump off)

I understand the car was imported from Italy to the US earlier this year and so I imagine it must have been in a running order to make it through import process. The car was listed on Craigslist for market value which was when my neighbor saw it and started making inquiries. He had arranged to go and see the vehicle but the seller contacted him and said car had developed a fault and wouldn't run right. The seller apparently took it to a mechanic who said he knew nothing of these type of cars. It reappeared on craigslist for roughly half the original price. My neighbor took the gamble and here we are....

Thanks dude for chiming in on this. The car is, and as far as I know, always was a negative earth. It definitely has been converted from a dynamo to an alternator and I can only assume the wiring has been done correctly - Ignition lights come on, starter motor turns and the engine will start so I imagine most electrical stuff is fundamentally OK. The coil looks newish and gives a decent spark on my tester - even when it won't start the spark looks strong. Ignition is points based but again I can't see anything wrong with them.

The owner drained the gas from the tank 2 weeks ago when he bought it (not sure about it being ethanol free). Yesterday I dismantled the carb and gave it a good clean. I noticed that the reservoir bowl had no gas in it when I stripped it down so I double checked the float valve and also tested the fuel pump. I put a new fuel filter in it for good measure. I was pretty sure I had found and fixed my problem (I hadn't). Another thing I did notice on the carb was the fuel return from the reservoir had been capped by a blocking pipe. Not sure why someone would do this but I could not find any evidence of a return line going back to the fuel tank so I assumed it wasn't a recent thing. After all my efforts yesterday the car started strongly as normal, ran well at idle and revved responsively before it started to die around 30-60 seconds later. It never started again during my visit. The neighbor told me it fired right up about 2 hours later and again died. It is like the fuel reservoir fills up after a couple of hours and then the car only runs on the fuel that is in that tiny reservoir - as soon as that runs out it stalls. Of course I can not think of any logic to back that theory up (how would a reservoir fill up with the pump off)

I understand the car was imported from Italy to the US earlier this year and so I imagine it must have been in a running order to make it through import process. The car was listed on Craigslist for market value which was when my neighbor saw it and started making inquiries. He had arranged to go and see the vehicle but the seller contacted him and said car had developed a fault and wouldn't run right. The seller apparently took it to a mechanic who said he knew nothing of these type of cars. It reappeared on craigslist for roughly half the original price. My neighbor took the gamble and here we are....

Click to expand...

That description would point me to the fuel pump.

Is this a mechanical or electric pump?

What I have experienced on my Studebaker after 30 years of storage:
Hoses cracked.
Fuel pump diaphragm failed
Carburetor gummed up and dried out

My car sat indoors for 31 years. For the first 15 of that, it got started once or twice a year, got fully warmed up, then shut off and set up for storage again.

Many of the folks on the Studebaker forum run into things they don;t think about with today's electronic fuel injection systems.

The fuel filter belongs between the CARB and the FUEL PUMP on a mechanical pump.
Most carbs have a sintered brass filter internal as well as an external paper filter cartridge.
Too many people try to place the filter between the pump and the tank with a mechanical pump. The mechanical diaphragm style pump cannot overcome the additional resistance of the filter, especially when it gets dirty.

Did you replace the needle and seat on the carb?
Did you drain and clean the interior of the fuel tank?
Did you check to make sure the lines are CLEAR back to the fuel tank? (You can use compressed air to blow GENTLY back into the tank from the fuel pump suction side. If there is an in-tank filter, you MAY end up blowing it off.)
Replace ALL hoses on the fuel line with NEW. If the hose between the pump and tank has a crack, it cannot develop a vacuum and draw fuel from the tank.
Try pressurizing the TANK during operation to see if it continues to run past the 2-minute mark. This can be accomplished with your mouth, a McDonalds soda straw, and your hand. Do NOT use compressed air, as you may over-pressurize the tank and cause MORE problems.

That all being said, FIRST try removing the gas cap during operation to see if it stays running. It may have the wrong non-vented cap on it and not be allowing the fuel pump to overcome the vacuum in the tank.